On a small hill in a neighborhood on the outskirts of Tokyo, there was a little park. Six close girls had always played there together since they were young. However, when they were in the fourth grade, they had to change schools. The six of them made a "promise to bury a time capsule," but ultimately they failed to keep this promise and eventually separated. Four years later, now grown up, they live their own lives. Although each of them faces their own troubles and worries, the days pass, and one day, a miracle happens to them.